1. Field of the Invention
The present invention relates to an exhaust emission control device and, more particularly to an improvement in an exhaust emission control device including an HC (hydrocarbon) converting first catalytic converter mounted in close proximity to an engine, and an HC converting second catalytic converter connected to the first catalytic converter through an exhaust pipe.
2. Description of the Related Art
The first and second catalytic converters in a device of this type exhibit an HC converting ability, after the adsorption of HC after the starting of an engine and the subsequent desorption of HC are conducted.
In this case, since the first catalytic converter is mounted in close proximity to the engine, the first catalytic converter reaches an HC desorption-completion temperature within a relatively short time, and therefore, the first catalytic converter exhibits the HC converting ability within a relatively short time after the start of the engine.
However, in general, the second catalytic converter is disposed below a vehicle floor because of a limitation of space. Therefore, the second catalytic converter is spaced far away from the engine, the second catalytic converter takes a relatively long time to reach the HC desorption-completion temperature. As a result, a large amount of HC is adsorbed in the second catalytic converter, and on the other hand, a large amount of HC is desorbed therefrom. This causes a problem in which a large amount of HC discharged at a CT time in an FTP mode in the prior art device.